This invention relates in general to breathing apparatus and in particular to a new and useful filter case for respirator masks in which filter inserts are held replaceably by a holder engaged in the case wall.
A similar filter case has been disclosed by German Registered Design No. 71 16 675. The known filter case is used to hold filter inserts that have collars on their front faces, which rest against the edge of the filter case when the filter is inserted. A cover is screwed onto a male thread of the filter case and presses the filter collar tightly against the edge of the filter case.
If several filters, for example a gas filter and a dust filter, are to be fastened together in the filter case, a higher or deeper cover is necessary because of the greater overall height of the two filters, and thus presses both filters mutually tightly against the edge of the filter case. The individual filter inserts also have different structural heights depending on the design and purpose of use. When using the higher cover to hold only one filter insert or to hold several filter inserts that differ in overall height, there is an unnecessarily large space requirement for the filter case, which therefore becomes bulky and unwieldy.
On the other hand, if only one filter insert of distinctly greater structural height is to be used, the screw cover provided for it then runs into the filter insert before the screw thread can grip securely.
The use of the known respirator mask is therefore also compelled to stock and to use the corresponding screw covers for the use of various filter inserts of different structural heights.